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1. Distance determination method of dust particles using Rosetta OSIRIS NAC and WAC data

Author

Drolshagen, E., Ott, T., Koschny, D., Güttler, C., Tubiana, C., Agarwal, J., Sierks, H., Barbieri, C., Lamy, P.I., Rodrigo, R., Rickman, H., A'Hearn, M.F., Barucci, M.A., Bertaux, J.-L., Bertini, I., Cremonese, G., Deppo, V. Da, Davidsson, B., Debei, S., Cecco, M. De, Deller, J., Feller, C., Fornasier, S., Fulle, M., Gicquel, A., Groussin, O., Gutiérrez, P.J., Hofmann, M., Hviid, S.F., Ip, W.-H., Jorda, L., Keller, H.U., Knollenberg, J., Kramm, J.R., Kührt, E., Küppers, M., Lara, L.M., Lazzarin, M., Moreno, J.J. Lopez, Marzari, F., Naletto, G., Oklay, N., Shi, X., Thomas, N., and Poppe, B.

Published
2017
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2. The global shape, density and rotation of Comet 67P/Churyumov-Gerasimenko from preperihelion Rosetta/OSIRIS observations

Author

Jorda, L., Gaskell, R., Capanna, C., Hviid, S., Lamy, P., Ďurech, J., Faury, G., Groussin, O., Gutiérrez, P., Jackman, C., Keihm, S.J., Keller, H.U., Knollenberg, J., Kührt, E., Marchi, S., Mottola, S., Palmer, E., Schloerb, F.P., Sierks, H., Vincent, J.-B., A’Hearn, M.F., Barbieri, C., Rodrigo, R., Koschny, D., Rickman, H., Barucci, M.A., Bertaux, J.L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Güttler, C., Ip, W.-H., Kramm, J.R., Küppers, M., Lara, L.M., Lazzarin, M., Lopez Moreno, J.J., Marzari, F., Naletto, G., Oklay, N., Thomas, N., Tubiana, C., and Wenzel, K.-P.

Published
2016
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3. Seasonal variations in source regions of the dust jets on comet 67P/Churyumov-Gerasimenko

Author

German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Ministry of Science and Technology (Taiwan), Science and Technology Development Fund (Macau), Lai, IL, Ip, W. H., Lee, J.C., Lin, Zhong-Yi, Vincent, J.B., Oklay, N., Sierks, H., Barbieri, C, Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, Pedro J., Güttler, C., Hofmann, M., Hviid, S.F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Shi, X., Tubiana, C., Thomas, N, German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Ministry of Science and Technology (Taiwan), Science and Technology Development Fund (Macau), Lai, IL, Ip, W. H., Lee, J.C., Lin, Zhong-Yi, Vincent, J.B., Oklay, N., Sierks, H., Barbieri, C, Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, Pedro J., Güttler, C., Hofmann, M., Hviid, S.F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Shi, X., Tubiana, C., and Thomas, N

Abstract

We investigate the surface distribution of the source regions of dust jets on comet 67P/Churyumov-Gerasimenko as a function of time. Methods. The dust jet source regions were traced by the comprehensive imaging data set provided by the OSIRIS scientific camera. Results. We show in detail how the projected footpoints of the dust jets and hence the outgassing zone would move in consonance with the sunlit belt. Furthermore, a number of source regions characterized by repeated jet activity might be the result of local topographical variations or compositional heterogeneities. Conclusions. The spatial and temporal variations in source regions of the dust jets are influenced significantly by the seasonal effect. The strong dependence on the solar zenith angle and local time could be related to the gas sublimation process driven by solar insolation on a surface layer of low thermal inertia.© ESO 2019

Published
2019

4. Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs

Author

Attree, N., Groussin, O., Jorda, L., Nébouy, D., Thomas, N., Brouet, Y., Kührt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M. F., Auger, A.T., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Lowry, S., Marchi, S., Marzari, F., Mottola, S., Naletto, G., European Commission, State Secretariat for Education, Research and Innovation (Switzerland), German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, and Swedish National Space Agency

Subjects
Comets: general, Comets: individual: 67P/Churyumov-Gerasimenko, Methods: observational, individual: 67P/Churyumov-Gerasimenko [Comets], general [Comets], observational [Methods]
Abstract

Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., We directly measured twenty overhanging cliffs on the surface of comet 67P/Churyumov-Gerasimenko extracted from the latest shape model and estimated the minimum tensile strengths needed to support them against collapse under the comet's gravity. We find extremely low strengths of around 1 Pa or less (1 to 5 Pa, when scaled to a metre length). The presence of eroded material at the base of most overhangs, as well as the observed collapse of two features and the implied previous collapse of another, suggests that they are prone to failure and that the true material strengths are close to these lower limits (although we only consider static stresses and not dynamic stress from, for example, cometary activity). Thus, a tensile strength of a few pascals is a good approximation for the tensile strength of the 67P nucleus material, which is in agreement with previous work. We find no particular trends in overhang properties either with size over the ~10-100 m range studied here or location on the nucleus. There are no obvious differences, in terms of strength, height or evidence of collapse, between the populations of overhangs on the two cometary lobes, suggesting that 67P is relatively homogenous in terms of tensile strength. Low material strengths are supportive of cometary formation as a primordial rubble pile or by collisional fragmentation of a small body (tens of km)., his project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 686709. This work was supported by the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number 16.0008-2. The opinions expressed and arguments employed herein do not necessarily reflect the official view of the Swiss Government. OSIRIS was built by a consortium of the Max-Planck-Institut fur Sonnensystemforschung, Gottingen, Germany; the CISAS University of Padova, Italy; the Laboratoire d'Astrophysique de Marseille, France; the Instituto de Astrofisica de Andalucia, CSIC, Granada, the Universidad Politechnica de Madrid, Spain; the Department of Physics and Astronomy of Uppsala University, Sweden; and the Institut fur Datentechnik und Kommunikationsnetze der Technischen Universitat Braunschweig, Germany. The support of the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), Sweden (SNSB), and the ESA Technical Directorate is gratefully acknowledged. We thank the Rosetta Science Operations Centre and the Rosetta Mission Operations Centre for the successful rendezvous with comet 67P/Churyumov-Gerasimenko.

Published
2018

5. On deviations from free-radial outflow in the inner coma of comet 67P/Churyumov–Gerasimenko

Author

Swiss National Science Foundation, European Commission, Gerig, S. -B., Marschall, R., Thomas, N., Bertini, I., Bodewits, D., Davidsson, B., Fulle, M., Ip, W. H., Keller, H.U., Küppers, M., Preusker, F., Scholten, F., Su, C. C., Toth, I., Tubiana, C., Wu, J. -S., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Agarwal, J., Barucci, M.A., Bertaux, J.L., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Groussin, O., Gutiérrez, Pedro J., Güttler, C., Hviid, S.F., Jorda, L., Knollenberg, J., Kramm, J.R., Kührt, E., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Mottola, S., Naletto, G., Oklay, N., Vincent, J.B., Swiss National Science Foundation, European Commission, Gerig, S. -B., Marschall, R., Thomas, N., Bertini, I., Bodewits, D., Davidsson, B., Fulle, M., Ip, W. H., Keller, H.U., Küppers, M., Preusker, F., Scholten, F., Su, C. C., Toth, I., Tubiana, C., Wu, J. -S., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Agarwal, J., Barucci, M.A., Bertaux, J.L., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Groussin, O., Gutiérrez, Pedro J., Güttler, C., Hviid, S.F., Jorda, L., Knollenberg, J., Kramm, J.R., Kührt, E., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Mottola, S., Naletto, G., Oklay, N., and Vincent, J.B.

Abstract

The Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) onboard the European Space Agency's Rosetta spacecraft acquired images of comet 67P/Churyumov–Gerasimenko (67P) and its surrounding dust coma starting from May 2014 until September 2016. In this paper we present methods and results from analysis of OSIRIS images regarding the dust outflow in the innermost coma of 67P. The aim is to determine the global dust outflow behaviour and place constraints on physical processes affecting particles in the inner coma. We study the coma region right above the nucleus surface, spanning from the nucleus centre out to a distance of about 50 km comet centric distance (approximately 25 average comet radii). We primarily adopt an approach used by Thomas and Keller (1990) to study the dust outflow. We present the effects on azimuthally-averaged values of the dust reflectance of non-radial flow and non-point-source geometry, acceleration of dust particles, sublimation of icy dust particles after ejection from the surface, dust particle fragmentation, optical depth effects and the influence of gravitationally bound particles. All of these physical processes could modify the observed distribution of light scattered by the dust coma. In the image analysis, profiles of azimuthally averaged dust brightness as a function of impact parameter b (azimuthal average, “Ā-curve”) were fitted with a simple function that best fits the shape of our profile curves (f(b;u,v,w,z)=u/b+wb+z). The analytical fit parameters (u, v, w, z), which hold the key information about the dust outflow behaviour, were saved in a comprehensive database. Through statistical analysis of these information, we show that the spatial distribution of dust follows free-radial outflow behaviour (i.e. force-free radial outflow with constant velocity) beyond distances larger than ∼11.9 km from the comet centre, which corresponds to a relative distance of about 6 average comet radii from the comet centre. Hence

Published
2018

6. Meter-scale thermal contraction crack polygons on the nucleus of comet 67P/Churyumov-Gerasimenko

Author

German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Auger, A.T., Groussin, O., Jorda, L., El-Maarry, M. R., Bouley, S., Séjourné, A., Gaskell, R., Capanna, C., Davidsson, B., Marchi, S., Höfner, S., Lamy, P.L., Sierks, H., Barbieri, C., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., A'Hearn, M. F., Barucci, M.A., Bertaux, J.L., Bertini, I., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Knollenberg, J., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Massironi, M., Michalik, H., Naletto, G., Oklay, N., Pommerol, A., Sabau, L., Thomas, N., Tubiana, C., Vincent, J.B., Wenzel, K. -P., German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Auger, A.T., Groussin, O., Jorda, L., El-Maarry, M. R., Bouley, S., Séjourné, A., Gaskell, R., Capanna, C., Davidsson, B., Marchi, S., Höfner, S., Lamy, P.L., Sierks, H., Barbieri, C., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., A'Hearn, M. F., Barucci, M.A., Bertaux, J.L., Bertini, I., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Knollenberg, J., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Massironi, M., Michalik, H., Naletto, G., Oklay, N., Pommerol, A., Sabau, L., Thomas, N., Tubiana, C., Vincent, J.B., and Wenzel, K. -P.

Abstract

We report on the detection and characterization of more than 6300 polygons on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, using images acquired by the OSIRIS camera onboard Rosetta between August 2014 and March 2015. They are found in consolidated terrains and grouped in localized networks. They are present at all latitudes (from North to South) and longitudes (head, neck, and body), sometimes on pit walls or following lineaments. About 1.5% of the observed surface is covered by polygons. Polygons have an homogeneous size across the nucleus, with 90% of them in the size range 1 – 5 m and a mean size of 3.0 ± 1.4 m. They show different morphologies, depending on the width and depth of their trough. They are found in networks with 3- or 4-crack intersection nodes. The polygons observed on 67P are consistent with thermal contraction crack polygons formed by the diurnal or seasonal temperature variations in a hard (MPa) and consolidated sintered layer of water ice, located a few centimeters below the surface. Our thermal analysis shows an evolution of thermal contraction crack polygons according to the local thermal environment, with more evolved polygons (i.e. deeper and larger troughs) where the temperature and the diurnal and seasonal temperature range are the highest. Thermal contraction crack polygons are young surface morphologies that probably formed after the injection of 67P in the inner solar system, typically 100,000 years ago, and could be as young as a few orbital periods, following the decreasing of its perihelion distance in 1959 from 2.7 to 1.3 a.u. Meter scale thermal contraction crack polygons should be common features on the nucleus of Jupiter family comets.© 2017 Elsevier Inc.

Published
2018

7. Coma morphology of comet 67P controlled by insolation over irregular nucleus

Author

German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Shi, X., Hu, X., Mottola, S., Sierks, H., Keller, H.U., Rose, M., Güttler, C., Fulle, M., Fornasier, S., Agarwal, J., Pajola, M., Tubiana, C., Bodewits, D., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Barucci, M.A., Bertaux, J.L., Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., Groussin, O., Gutiérrez, Pedro J., Hviid, S.F., Ip, W. H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Oklay, N., Toth, I., Vincent, J.B., German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Shi, X., Hu, X., Mottola, S., Sierks, H., Keller, H.U., Rose, M., Güttler, C., Fulle, M., Fornasier, S., Agarwal, J., Pajola, M., Tubiana, C., Bodewits, D., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Barucci, M.A., Bertaux, J.L., Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., Groussin, O., Gutiérrez, Pedro J., Hviid, S.F., Ip, W. H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Oklay, N., Toth, I., and Vincent, J.B.

Abstract

While the structural complexity of cometary comae is already recognizable from telescopic observations, the innermost region, within a few radii of the nucleus, was not resolved until spacecraft exploration became a reality. The dust coma displays jet-like features of enhanced brightness superposed on a diffuse background . Some features can be traced to specific areas on the nucleus, and result conceivably from locally enhanced outgassing and/or dust emission. However, diffuse or even uniform activity over topographic concavity can converge to produce jet-like features. Therefore, linking observed coma morphology to the distribution of activity on the nucleus is difficult. Here, we study the emergence of dust activity at sunrise on comet 67P/Churyumov-Gerasimenko using high-resolution, stereo images from the OSIRIS camera onboard the Rosetta spacecraft, where the sources and formation of the jet-like features are resolved. We perform numerical simulations to show that the ambient dust coma is driven by pervasive but non-uniform water outgassing from the homogeneous surface layer. Physical collimations of gas and dust flows occur at local maxima of insolation and also via topographic focusing. Coma structures are projected to exhibit jet-like features that vary with the perspective of the observer. For an irregular comet such as 67P/Churyumov-Gerasimenko, near-nucleus coma structures can be concealed in the shadow of the nucleus, which further complicates the picture.© 2018 The Author(s).

Published
2018

8. Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs

Author

European Commission, State Secretariat for Education, Research and Innovation (Switzerland), German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Attree, N., Groussin, O., Jorda, L., Nébouy, D., Thomas, N., Brouet, Y., Kührt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M. F., Auger, A.T., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Lowry, S., Marchi, S., Marzari, F., Mottola, S., Naletto, G., European Commission, State Secretariat for Education, Research and Innovation (Switzerland), German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Attree, N., Groussin, O., Jorda, L., Nébouy, D., Thomas, N., Brouet, Y., Kührt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M. F., Auger, A.T., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Lowry, S., Marchi, S., Marzari, F., Mottola, S., and Naletto, G.

Abstract

We directly measured twenty overhanging cliffs on the surface of comet 67P/Churyumov-Gerasimenko extracted from the latest shape model and estimated the minimum tensile strengths needed to support them against collapse under the comet's gravity. We find extremely low strengths of around 1 Pa or less (1 to 5 Pa, when scaled to a metre length). The presence of eroded material at the base of most overhangs, as well as the observed collapse of two features and the implied previous collapse of another, suggests that they are prone to failure and that the true material strengths are close to these lower limits (although we only consider static stresses and not dynamic stress from, for example, cometary activity). Thus, a tensile strength of a few pascals is a good approximation for the tensile strength of the 67P nucleus material, which is in agreement with previous work. We find no particular trends in overhang properties either with size over the ~10-100 m range studied here or location on the nucleus. There are no obvious differences, in terms of strength, height or evidence of collapse, between the populations of overhangs on the two cometary lobes, suggesting that 67P is relatively homogenous in terms of tensile strength. Low material strengths are supportive of cometary formation as a primordial rubble pile or by collisional fragmentation of a small body (tens of km).

Published
2018

9. The phase function and density of the dust observed at comet 67P/Churyumov-Gerasimenko

Author

Agenzia Spaziale Italiana, Fulle, M., Bertini, I., Della Corte, V., Güttler, C., Ivanovski, S., La Forgia, F., Lasue, J., Levasseur-Regourd, A. C., Marzari, F., Moreno, Fernando, Mottola, S., Naletto, G., Palumbo, P., Rinaldi, G., Rotundi, A., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Barucci, M.A., Bertaux, J.L., Bodewits, D., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Groussin, O., Gutiérrez, Pedro J., Hviid, H.S., Ip, W. H., Jorda, L., Keller, H.U., Knollenberg, J., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Shi, X., Thomas, N., Tubiana, C., Agenzia Spaziale Italiana, Fulle, M., Bertini, I., Della Corte, V., Güttler, C., Ivanovski, S., La Forgia, F., Lasue, J., Levasseur-Regourd, A. C., Marzari, F., Moreno, Fernando, Mottola, S., Naletto, G., Palumbo, P., Rinaldi, G., Rotundi, A., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Barucci, M.A., Bertaux, J.L., Bodewits, D., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fornasier, S., Groussin, O., Gutiérrez, Pedro J., Hviid, H.S., Ip, W. H., Jorda, L., Keller, H.U., Knollenberg, J., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Shi, X., Thomas, N., and Tubiana, C.

Abstract

The OSIRIS camera onboard Rosetta measured the phase function of both the coma dust and the nucleus. The two functions have a very different slope versus the phase angle. Here, we show that the nucleus phase function should be adopted to convert the brightness to the size of dust particles larger than 2.5 mm only. This makes the dust bursts observed close to Rosetta by OSIRIS, occurring about every hour, consistent with the fragmentation on impact with Rosetta of parent particles, whose flux agrees with the dust flux observed by GIADA. OSIRIS also measured the antisunward acceleration of the fragments, thus providing the first direct measurement of the solar radiation force acting on the dust fragments and thus of their bulk density, excluding any measurable rocket effect by the ice sublimation from the dust. The obtained particle density distribution has a peak matching the bulk density of most COSIMA particles, and represents a subset of the density distribution measured by GIADA. This implies a bias in the elemental abundances measured by COSIMA, which thus are consistent with the 67P dust mass fractions inferred by GIADA, i.e. (38 ± 8) per cent of hydrocarbons versus the (62 ± 8) per cent of sulphides and silicates.© 2018 The Author(s).Published by Oxford University Press on behalf of the Royal Astronomical Society.

Published
2018

10. Opposition effect on comet 67P/Churyumov-Gerasimenko using Rosetta-OSIRIS images

Author

Swedish National Space Board, Ministerio de Economía y Competitividad (España), Agenzia Spaziale Italiana, Centre National de la Recherche Scientifique (France), German Centre for Air and Space Travel, European Space Agency, Masoumzadeh, N., Oklay, N., Kolokolova, L., Sierks, H., Fornasier, S., Barucci, M.A., Vincent, J.B., Tubiana, C., Güttler, C., Preusker, F., Scholten, F., Mottola, S., Hasselmann, P.H., Feller, C., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., A'Hearn, M. F., Bertaux, J.L., Bertini, I., Cremonese, G., Da Deppo, Vania, Davidsson, Björn J. R., Debei, S., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutiérrez, Pedro J., Hall, I., Hofmann, M., Hviid, S.F., Ip, W. H., Jorda, L., Keller, H.U., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Shi, X., Thomas, N., Swedish National Space Board, Ministerio de Economía y Competitividad (España), Agenzia Spaziale Italiana, Centre National de la Recherche Scientifique (France), German Centre for Air and Space Travel, European Space Agency, Masoumzadeh, N., Oklay, N., Kolokolova, L., Sierks, H., Fornasier, S., Barucci, M.A., Vincent, J.B., Tubiana, C., Güttler, C., Preusker, F., Scholten, F., Mottola, S., Hasselmann, P.H., Feller, C., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., A'Hearn, M. F., Bertaux, J.L., Bertini, I., Cremonese, G., Da Deppo, Vania, Davidsson, Björn J. R., Debei, S., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutiérrez, Pedro J., Hall, I., Hofmann, M., Hviid, S.F., Ip, W. H., Jorda, L., Keller, H.U., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Shi, X., and Thomas, N.

Abstract

Aims. We aim to explore the behavior of the opposition effect as an important tool in optical remote sensing on the nucleus of comet 67P/Churyumov-Gerasimenko (67P), using Rosetta-OSIRIS images acquired in different filters during the approach phase, July-August 2014 and the close flyby images on 14 of February 2015, which contain the spacecraft shadow. Methods. We based our investigation on the global and local brightness from the surface of 67P with respect to the phase angle, also known as phase curve. The local phase curve corresponds to a region that is located at the Imhotep-Ash boundary of 67P. Assuming that the region at the Imhotep-Ash boundary and the entire nucleus have similar albedo, we combined the global and local phase curves to study the opposition-surge morphology and constrain the structure and properties of 67P. The model parameters were furthermore compared with other bodies in the solar system and existing laboratory study. Results. We found that the morphological parameters of the opposition surge decrease monotonically with wavelength, whereas in the case of coherent backscattering this behavior should be the reverse. The results from comparative analysis place 67P in the same category as the two Mars satellites, Phobos and Deimos, which are notably different from all airless bodies in the solar system. The similarity between the surface phase function of 67P and a carbon soot sample at extremely small angles is identified, introducing regolith at the boundary of the Imhotep-Ash region of 67P as a very dark and fluffy layer.© ESO, 2017.

Published
2017

11. Seasonal erosion and restoration of the dust cover on comet 67P/Churyumov-Gerasimenko as observed by OSIRIS onboard Rosetta

Author

European Space Agency, Centre National de la Recherche Scientifique (France), Agenzia Spaziale Italiana, Swedish National Space Board, Ministerio de Economía y Competitividad (España), International Max Planck Research Schools, German Centre for Air and Space Travel, Hu, X., Shi, X., Sierks, H., Fulle, M., Blum, J., Keller, H.U., Kührt, E., Davidsson, B., Güttler, C., Gundlach, B., Pajola, M., Bodewits, D., Vincent, J.B., Oklay, N., Massironi, M., Fornasier, S., Tubiana, C., Groussin, O., Boudreault, S., Höfner, S., Mottola, S., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., A'Hearn, M. F., Agarwal, J., Barucci, M.A., Bertaux, J.L., Bertini, I., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Gicquel, A., Gutierrez-Marques, P., Gutiérrez, Pedro J., Hofmann, M., Hviid, S.F., Ip, W. H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, López-Moreno, José Juan, European Space Agency, Centre National de la Recherche Scientifique (France), Agenzia Spaziale Italiana, Swedish National Space Board, Ministerio de Economía y Competitividad (España), International Max Planck Research Schools, German Centre for Air and Space Travel, Hu, X., Shi, X., Sierks, H., Fulle, M., Blum, J., Keller, H.U., Kührt, E., Davidsson, B., Güttler, C., Gundlach, B., Pajola, M., Bodewits, D., Vincent, J.B., Oklay, N., Massironi, M., Fornasier, S., Tubiana, C., Groussin, O., Boudreault, S., Höfner, S., Mottola, S., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., A'Hearn, M. F., Agarwal, J., Barucci, M.A., Bertaux, J.L., Bertini, I., Cremonese, G., Da Deppo, Vania, Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Gicquel, A., Gutierrez-Marques, P., Gutiérrez, Pedro J., Hofmann, M., Hviid, S.F., Ip, W. H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, and López-Moreno, José Juan

Abstract

Context. Dust deposits or dust cover are a prevalent morphology in the northern hemi-nucleus of comet 67P/Churyumov-Gerasimenko (67P). The evolution of the dust deposits was captured by the OSIRIS camera system onboard the Rosetta spacecraft having escorted the comet for over two years. The observations shed light on the fundamental role of cometary activity in shaping and transforming the surface morphology. Aims. We aim to present OSIRIS observations of surface changes over the dust deposits before and after perihelion. The distribution of changes and a timeline of their occurrence are provided. We perform a data analysis to quantify the surface changes and investigate their correlation to water activity from the dust deposits. We further discuss how the results of our investigation are related to other findings from the Rosetta mission. Methods. Surface changes were detected via systematic comparison of images, and quantified using shape-from-shading technique. Thermal models were applied to estimate the erosion of water ice in response to the increasing insolation over the areas where surface changes occurred. Modeling results were used for the interpretation of the observed surface changes. Results. Surface changes discussed here were concentrated at mid-latitudes, between about 20â-N and 40â-N, marking a global transition from the dust-covered to rugged terrains. The changes were distributed in open areas exposed to ample solar illumination and likely subject to enhanced surface erosion before perihelion. The occurrence of changes followed the southward migration of the sub-solar point across the latitudes of their distribution. The erosion at locations of most changes was at least about 0.5 m, but most likely did not exceed several meters. The erosive features before perihelion had given way to a fresh, smooth cover of dust deposits after perihelion, suggesting that the dust deposits had been globally restored by at least about 1 m with ejecta from the intens

Published
2017

12. Evidence of sub-surface energy storage in comet 67P from the outburst of 2016 July 03

Author

Centre National de la Recherche Scientifique (France), German Centre for Air and Space Travel, Agenzia Spaziale Italiana, Swedish National Space Board, Ministerio de Economía y Competitividad (España), European Space Agency, Agarwal, J., Della Corte, V., Feldman, P. D., Geiger, B., Merouane, S., Bertini, I., Bodewits, D., Fornasier, S., Grün, E., Hasselmann, P.H., Hilchenbach, M., Höfner, S., Ivanovski, S., Kolokolova, L., Pajola, M., Rotundi, A., Sierks, H., Steffl, A. J., Thomas, N., A'Hearn, M. F., Barbieri, C., Barucci, M.A., Bertaux, J.L., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J. F., Feaga, L. M., Fischer, H., Fulle, M., Gicquel, A., Groussin, O., Güttler, C., Gutiérrez, Pedro J., Hofmann, M., Hornung, K., Hviid, S.F., Ip, W. H., Jorda, L., Keller, H.U., Kissel, J., Knollenberg, J., Koch, A., Koschny, D., Kramm, J.R., Kührt, E., Küppers, M., Langevin, Y., Lara, Luisa María, López-Moreno, José Juan, Rodrigo Montero, Rafael, Centre National de la Recherche Scientifique (France), German Centre for Air and Space Travel, Agenzia Spaziale Italiana, Swedish National Space Board, Ministerio de Economía y Competitividad (España), European Space Agency, Agarwal, J., Della Corte, V., Feldman, P. D., Geiger, B., Merouane, S., Bertini, I., Bodewits, D., Fornasier, S., Grün, E., Hasselmann, P.H., Hilchenbach, M., Höfner, S., Ivanovski, S., Kolokolova, L., Pajola, M., Rotundi, A., Sierks, H., Steffl, A. J., Thomas, N., A'Hearn, M. F., Barbieri, C., Barucci, M.A., Bertaux, J.L., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J. F., Feaga, L. M., Fischer, H., Fulle, M., Gicquel, A., Groussin, O., Güttler, C., Gutiérrez, Pedro J., Hofmann, M., Hornung, K., Hviid, S.F., Ip, W. H., Jorda, L., Keller, H.U., Kissel, J., Knollenberg, J., Koch, A., Koschny, D., Kramm, J.R., Kührt, E., Küppers, M., Langevin, Y., Lara, Luisa María, López-Moreno, José Juan, and Rodrigo Montero, Rafael

Abstract

On 2016 July 03, several instruments onboard ESA's Rosetta spacecraft detected signs of an outburst event on comet 67P, at a heliocentric distance of 3.32 au from the Sun, outbound from perihelion. We here report on the inferred properties of the ejected dust and the surface change at the site of the outburst. The activity coincided with the local sunrise and continued over a time interval of 14-68 min. It left a 10-m-sized icy patch on the surface. The ejected material comprised refractory grains of several hundred microns in size, and sub-micron-sized water ice grains. The high dust mass production rate is incompatible with the free sublimation of crystalline water ice under solar illumination as the only acceleration process. Additional energy stored near the surface must have increased the gas density. We suggest a pressurized sub-surface gas reservoir, or the crystallization of amorphous water ice as possible causes.© 2015 The Authors.

Published
2017

13. Characterization of dust aggregates in the vicinity of the Rosetta spacecraft

Author

Swedish National Space Board, Ministerio de Economía y Competitividad (España), German Centre for Air and Space Travel, Agenzia Spaziale Italiana, Centre National de la Recherche Scientifique (France), European Space Agency, Güttler, C., Hasselmann, P.H., Li, Y., Fulle, M., Tubiana, C., Kovacs, G., Agarwal, J., Sierks, H., Fornasier, S., Hofmann, M., Gutiérrez Marqués, P., Ott, T., Drolshagen, E., Bertini, I., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., A'Hearn, M. F., Barucci, M.A., Bodewits, D., Bertaux, J.L., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., Geiger, B., Groussin, O., Gutiérrez, Pedro J., Hviid, S.F., Ip, W. H., Jorda, L., Keller, H.U., Knollenberg, J., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Swedish National Space Board, Ministerio de Economía y Competitividad (España), German Centre for Air and Space Travel, Agenzia Spaziale Italiana, Centre National de la Recherche Scientifique (France), European Space Agency, Güttler, C., Hasselmann, P.H., Li, Y., Fulle, M., Tubiana, C., Kovacs, G., Agarwal, J., Sierks, H., Fornasier, S., Hofmann, M., Gutiérrez Marqués, P., Ott, T., Drolshagen, E., Bertini, I., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., A'Hearn, M. F., Barucci, M.A., Bodewits, D., Bertaux, J.L., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., Geiger, B., Groussin, O., Gutiérrez, Pedro J., Hviid, S.F., Ip, W. H., Jorda, L., Keller, H.U., Knollenberg, J., Kramm, J.R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Mottola, S., Naletto, G., Oklay, N., and Pajola, M.

Abstract

In a Rosetta/OSIRIS imaging activity in 2015 June, we have observed the dynamic motion of particles close to the spacecraft. Due to the focal setting of the OSIRIS wide angle camera, these particles were blurred, which can be used to measure their distances to the spacecraft. We detected 109 dust aggregates over a 130 min long sequence, and find that their sizes are around a millimetre and their distances cluster between 2 and 40 m from the spacecraft. Their number densities are about a factor 10 higher than expected for the overall coma and highly fluctuating. Their velocities are small compared to the spacecraft orbital motion and directed away from the spacecraft, towards the comet. From this we conclude that they have interacted with the spacecraft and assess three possible scenarios. In the likeliest of the three scenarios, centimetre-sized aggregates collide with the spacecraft and we would observe the fragments. Ablation of a dust layer on the spacecraft's z panel (remote instrument viewing direction) when rotated towards the Sun is a reasonable alternative. We could also measure an acceleration for a subset of 18 aggregates, which is directed away from the Sun and can be explain by a rocket effect, which requires a minimum ice fraction of the order of 0.1 per cent.© 2017 The Authors.

Published
2017

14. Temporal morphological changes in the Imhotep region of comet 67P/Churyumov-Gerasimenko

Author

Groussin, O., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M.F., Auger, A.-T., Barucci, M.A., Bertaux, J.-L., Bertini, I., Besse, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., El-Maarry, M.R., Fornasier, S., Fulle, M., Gutiérrez, P.J., Güttler, C., Hviid, S., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, L.M., Lazzarin, M., Lopez Moreno, J.J., Lowry, S., Marchi, S., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Thomas, N., Toth, I., Tubiana, C., Vincent, J.-B., Groussin, O., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M.F., Auger, A.-T., Barucci, M.A., Bertaux, J.-L., Bertini, I., Besse, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., El-Maarry, M.R., Fornasier, S., Fulle, M., Gutiérrez, P.J., Güttler, C., Hviid, S., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, L.M., Lazzarin, M., Lopez Moreno, J.J., Lowry, S., Marchi, S., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Thomas, N., Toth, I., Tubiana, C., and Vincent, J.-B.

Abstract

Aims. We report on the first major temporal morphological changes observed on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko in the smooth terrains of the Imhotep region. Methods. We used images of the OSIRIS cameras onboard Rosetta to follow the temporal changes from 24 May 2015 to 11 July 2015. Results. The morphological changes observed on the surface are visible in the form of roundish features that are growing in size from a given location in a preferential direction at a rate of 5.6-8.1 x 10-5 m s-1 during the observational period. The location where the changes started and the contours of the expanding features are bluer than the surroundings, which suggests that ices (H2O and/or CO2) are exposed on the surface. However, sublimation of ices alone is not sufficient to explain the observed expanding features. No significant variations in the dust activity pattern are observed during the period of changes. © ESO, 2015.

Published
2015

16. E-type asteroid (2867) steins as imaged by OSIRIS on board rosetta

Author

Keller, H.U., Barbieri, C., Koschny, D., Lamy, P., Rkkman, H., Rodrigo, R., Sierks, H., A'Hearn, M.F., Angrilli, F., Barucci, M.A., Bertaux, J.-L., Cremonese, G., Da Deppo, V., Davidsson, B., De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, P.J., Hviid, S.F., Ip, W.-H., Jorda, L., Knollenberg, J., Kramm, J.R., Kührt, E., Küppers, M., Lara, L.-M., Lazzarin, M., Lopez Moreno, J., Marzari, F., Michalik, H., Naletto, G., Sabau, L., Thomas, N., Wenzel, K.-P., Bertini, I., Besse, S., Ferri, F., Kaasalainen, M., Lowry, S.C., Marchi, S., Mottola, S., Sabolo, W., Schröder, S.E., Spjuth, S., Vernazza, P., Keller, H.U., Barbieri, C., Koschny, D., Lamy, P., Rkkman, H., Rodrigo, R., Sierks, H., A'Hearn, M.F., Angrilli, F., Barucci, M.A., Bertaux, J.-L., Cremonese, G., Da Deppo, V., Davidsson, B., De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, P.J., Hviid, S.F., Ip, W.-H., Jorda, L., Knollenberg, J., Kramm, J.R., Kührt, E., Küppers, M., Lara, L.-M., Lazzarin, M., Lopez Moreno, J., Marzari, F., Michalik, H., Naletto, G., Sabau, L., Thomas, N., Wenzel, K.-P., Bertini, I., Besse, S., Ferri, F., Kaasalainen, M., Lowry, S.C., Marchi, S., Mottola, S., Sabolo, W., Schröder, S.E., Spjuth, S., and Vernazza, P.

Abstract

The European Space Agency's Rosetta mission encountered the main-belt asteroid (2867) Steins while on its way to rendezvous with comet 67P/Churyumov-Gerasimenko. Images taken with the OSIRIS (optical, spectroscopic, and infrared remote imaging system) cameras on board Rosetta show that Steins is an oblate body with an effective spherical diameter of 5.3 kilometers. Its surface does not show color variations. The morphology of Steins is dominated by linear faults and a large 2.1-kilometer-diameter crater near its south pole. Crater counts reveal a distinct lack of small craters. Steins is not solid rock but a rubble pile and has a conical appearance that is probably the result of reshaping due to Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) spin-up. The OSIRIS images constitute direct evidence for the YORP effect on a main-belt asteroid.

Published
2010

17. A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2

Author

Snodgrass, C., Tubiana, C., Vincent, J.-B., Sierks, H., Hviid, S., Moissl, R., Boehnhardt, H., Barbieri, C., Koschny, D., Lamy, P., Rickman, H., Rodrigo, R., Carry, B., Lowry, S.C., Laird, R.J.M., Weissman, P.R., Fitzsimmons, A., Marchi, S., A'Hearn, M., Angrilli, F., Barucci, A., Bertaux, J.-L., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Fornasier, S., Gutiérrez, P., Ip, W.-H., Keller, H.U., Knollenberg, J., Kramm, J.R., Kuehrt, E., Kueppers, M., Lara, L.M., Lazzarin, M., López-Moreno, J.J., Marzari, F., Michalik, H., Naletto, G., Sabau, L., Thomas, N., Wenzel, K.P., Snodgrass, C., Tubiana, C., Vincent, J.-B., Sierks, H., Hviid, S., Moissl, R., Boehnhardt, H., Barbieri, C., Koschny, D., Lamy, P., Rickman, H., Rodrigo, R., Carry, B., Lowry, S.C., Laird, R.J.M., Weissman, P.R., Fitzsimmons, A., Marchi, S., A'Hearn, M., Angrilli, F., Barucci, A., Bertaux, J.-L., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Fornasier, S., Gutiérrez, P., Ip, W.-H., Keller, H.U., Knollenberg, J., Kramm, J.R., Kuehrt, E., Kueppers, M., Lara, L.M., Lazzarin, M., López-Moreno, J.J., Marzari, F., Michalik, H., Naletto, G., Sabau, L., Thomas, N., and Wenzel, K.P.

Abstract

The peculiar object P/2010 A2 was discovered1 in January 2010 and given a cometary designation because of the presence of a trail of material, although there was no central condensation or coma. The appearance of this object, in an asteroidal orbit (small eccentricity and inclination) in the inner main asteroid belt attracted attention as a potential new member of the recently recognized2 class of main-belt comets. If confirmed, this new object would expand the range in heliocentric distance over which main-belt comets are found. Here we report observations of P/2010 A2 by the Rosetta spacecraft. We conclude that the trail arose from a single event, rather than a period of cometary activity, in agreement with independent results3. The trail is made up of relatively large particles of millimetre to centimetre size that remain close to the parent asteroid. The shape of the trail can be explained by an initial impact ejecting large clumps of debris that disintegrated and dispersed almost immediately. We determine that this was an asteroid collision that occurred around 10 February 2009. © 2010 Macmillan Publishers Limited. All rights reserved.

Published
2010

18. OSIRIS – The scientific camera system onboard Rosetta

Author

Keller, H. U., Barbieri, C., Lamy, P., Rickman, H., Rodrigo, R., Wenzel, K. P., Sierks, H., A'Hearn, Michael F., Angrilli, F., Angulo, M., Bailey, M. E., Barthol, P., Barucci, M.A., Bertaux, J. L., Bianchini, G., Boit, J. L., Brown, V., Burns, J. A., Büttner, I., Castro, J. M., Cremonese, G., Curdt, W., Deppo, V., Debei, S., De Cecco, M., Dohlen, K., Fornasier, S., Fulle, M., Germerott, D., Gliem, M., Guizzo, G.P., Hviid, S.F., IP, W.H., Jorda, L., Koschiny, D., Kramm, J.R., Khürt, E., Küpers, M., Lara, L.M., Llebaria, A., López, A., López-Jiménez, A., López-Moreno, J., Meller, R., Michalik, H., Michelena, M.D., Müller, R., Naletto, G., Origne, A., Parzianello, G., Pertile, M., Quintana, C., Ragazzoni, R., Ramous, P., Reiche, K.U., Reina, M., Rodríguez, J., Rousset, G., Sabau, L., Sanz Andres, Angel Pedro, Sivan, J. P., Stöckner, K., Tabero, J., Telljohann, U., Thomas, N., Timon, V., Tomasch, G., Wittrock, T., Zaccariotto, M., Keller, H. U., Barbieri, C., Lamy, P., Rickman, H., Rodrigo, R., Wenzel, K. P., Sierks, H., A'Hearn, Michael F., Angrilli, F., Angulo, M., Bailey, M. E., Barthol, P., Barucci, M.A., Bertaux, J. L., Bianchini, G., Boit, J. L., Brown, V., Burns, J. A., Büttner, I., Castro, J. M., Cremonese, G., Curdt, W., Deppo, V., Debei, S., De Cecco, M., Dohlen, K., Fornasier, S., Fulle, M., Germerott, D., Gliem, M., Guizzo, G.P., Hviid, S.F., IP, W.H., Jorda, L., Koschiny, D., Kramm, J.R., Khürt, E., Küpers, M., Lara, L.M., Llebaria, A., López, A., López-Jiménez, A., López-Moreno, J., Meller, R., Michalik, H., Michelena, M.D., Müller, R., Naletto, G., Origne, A., Parzianello, G., Pertile, M., Quintana, C., Ragazzoni, R., Ramous, P., Reiche, K.U., Reina, M., Rodríguez, J., Rousset, G., Sabau, L., Sanz Andres, Angel Pedro, Sivan, J. P., Stöckner, K., Tabero, J., Telljohann, U., Thomas, N., Timon, V., Tomasch, G., Wittrock, T., and Zaccariotto, M.

Abstract

The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS is the scientific camera system onboard the Rosetta spacecraft (Figure 1). The advanced high performance imaging system will be pivotal for the success of the Rosetta mission. OSIRIS will detect 67P/Churyumov-Gerasimenko from a distance of more than 106 km, characterise the comet shape and volume, its rotational state and find a suitable landing spot for Philae, the Rosetta lander. OSIRIS will observe the nucleus, its activity and surroundings down to a scale of ~2 cm px−1. The observations will begin well before the onset of cometary activity and will extend over months until the comet reaches perihelion. During the rendezvous episode of the Rosetta mission, OSIRIS will provide key information about the nature of cometary nuclei and reveal the physics of cometary activity that leads to the gas and dust coma. OSIRIS comprises a high resolution Narrow Angle Camera (NAC) unit and a Wide Angle Camera (WAC) unit accompanied by three electronics boxes. The NAC is designed to obtain high resolution images of the surface of comet 7P/Churyumov-Gerasimenko through 12 discrete filters over the wavelength range 250–1000 nm at an angular resolution of 18.6 μrad px−1. The WAC is optimised to provide images of the near-nucleus environment in 14 discrete filters at an angular resolution of 101 μrad px−1. The two units use identical shutter, filter wheel, front door, and detector systems. They are operated by a common Data Processing Unit. The OSIRIS instrument has a total mass of 35 kg and is provided by institutes from six European countries

Published
2007

19. Osiris— The optical, spectroscopic and infrared remote imaging system for the Rosetta orbiter

Author

Thomas, N., Keller, H. U., Arijs, E., Barbieri, C., Grande, M., Lamy, P., Rickman, H., Rodrigo, R., Wenzel, K. P., A'Hearn, Michael F., Angrilli, F., Bailey, M. E., Barucci, M.A., Bertaux, J. L., Brieb, K., Burns, J. A., Cremonese, G., Curdt, W., Deceunick, H., Emery, R., Festou, M., Fulle, M., Ip, Wing, Jorda, L., Korth, A., Koschny, Detlef, Kramm, J.R., Kürth, Ekkehard, Lara, L.M., Llebaria, A., López Moreno, José Luis, Marzari, Francesco, Moreau, L., Muller, Claas, Murray, C., Naletto, G., Nevejans, D., Ragazzoni, R., Sabau, L., Sanz Andres, Angel Pedro, Sivan, J. P., Tondello, G., Thomas, N., Keller, H. U., Arijs, E., Barbieri, C., Grande, M., Lamy, P., Rickman, H., Rodrigo, R., Wenzel, K. P., A'Hearn, Michael F., Angrilli, F., Bailey, M. E., Barucci, M.A., Bertaux, J. L., Brieb, K., Burns, J. A., Cremonese, G., Curdt, W., Deceunick, H., Emery, R., Festou, M., Fulle, M., Ip, Wing, Jorda, L., Korth, A., Koschny, Detlef, Kramm, J.R., Kürth, Ekkehard, Lara, L.M., Llebaria, A., López Moreno, José Luis, Marzari, Francesco, Moreau, L., Muller, Claas, Murray, C., Naletto, G., Nevejans, D., Ragazzoni, R., Sabau, L., Sanz Andres, Angel Pedro, Sivan, J. P., and Tondello, G.

Abstract

The scientific objectives, design, and implementation of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) for the International Rosetta Mission are described. The instrument comprises two camera systems with a common electronics box. A narrow angle camera will provide high resolution images of the structure and morphology of the nucleus of a comet. A wide angle camera with high straylight rejection and dynamic range will be used to investigate the innermost coma and the emission process at the surface of the comet. An infrared imaging system, which dramatically enhances the scientific return has been included in the narrow angle camera at little extra cost.

Published
1998

21. The global shape, density and rotation of Comet 67P/Churyumov-Gerasimenko from preperihelion Rosetta/OSIRIS observations

Author

Fulle, M., Davidsson, B., Groussin, O., Bertaux, J.L., Barbieri, C., Ďurech, J., Gaskell, R., Da Deppo, V., Kührt, E., Lara, L.M., Oklay, N., Kramm, J.R., Marchi, S., Schloerb, F.P., Fornasier, S., Rickman, H., A’Hearn, M.F., Marzari, F., Ip, W.-H., Jorda, L., Lopez Moreno, J.J., Capanna, C., Rodrigo, R., Güttler, C., Lazzarin, M., Cremonese, G., Keller, H.U., Mottola, S., Keihm, S.J., Barucci, M.A., De Cecco, M., Thomas, Nicolas, Faury, G., Bertini, I., Wenzel, K.-P., Küppers, M., Naletto, G., Palmer, E., Gutiérrez, P., Vincent, J.-B., Jackman, C., Knollenberg, J., Koschny, D., Sierks, H., Tubiana, C., Hviid, S., Debei, S., and Lamy, P.

Subjects
13. Climate action, 530 Physics, 500 Science
Abstract

The Rosetta spacecraft reached Comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) in August 2014 at an heliocentric distance of 3.6 a.u. and was then put in orbit around its nucleus to perform detailed observations. Among the collected data are the images acquired by the OSIRIS instrument up to the perihelion passage of the comet in August 2015, which allowed us to map the entire nucleus surface at high-resolution in the visible. Stereophotoclinometry methods have been used to reconstruct a global high-resolution shape model and to monitor its rotational parameters using data collected up to perihelion. The nucleus has a conspicuous bilobate shape with overall dimensions along its principal axes of (4.34 + 0.02) x (2.60 + 0.02) x (2.12 + 0.06) km. The best-fit ellipsoid dimensions of the individual lobes along their principal axes of inertia are found to be 4.10 x 3.52 x 1.63 km and 2.50 x 2.14 x 1.641cm. Their volume amounts to 66% and 27% of the total volume of the nucleus. The two lobes are connected by a "neck" whose volume has been estimated to represent similar to 7% of the total volume of the comet. Combining the derived volume of 18.8 + 0.3 km(3) with the mass of 9.982 + 0.003 x 10(12) kg determined by the Rosetta/RSI experiment, we obtained a bulk density of the nucleus of 532 + 7 kg m⁻³. Together with the companion value of 535 35 kg m⁻³ deduced from the stereophotogrammetry shape model of the nucleus (Preusker et al. [2015] Astron. Astrophys. 583, A33), these constitute the first reliable and most accurate determination of the density of a cometary nucleus to date. The calculated porosity is quite large, ranging approximately from 70% to 75% depending upon the assumed density of the dust grains and the dust-to-ice mass ratio. The nature of the porosity, either micro or macro or both, remains unconstrained. The coordinates of the center of gravity are not compatible with a uniform nucleus density. The direction of the offset between the center of gravity and the center of figure suggests that the big lobe has a slightly higher bulk density compared to the small one. the center of mass position cannot be explained by different, but homogenous densities in the two lobes. The initial rotational period of 12.4041 + 0.0001 h of the nucleus persisted until October 2014. It then slightly increased to a maximum of 12.4304h reached on 19 May 2015 and finally dropped to 12.305 h just before perihelion on August 10, 2015. A periodogram analysis of the (RA, Dec) direction of the Z-axis of the comet obtained in parallel with the shape reconstruction exhibits a highly significant minima at 11.5 + 0.5 day clearly indicating an excited rotational state with an amplitude of 0.15 + 0.03 degrees.

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